Many therapeutic procedures can be performed percutaneously. Such procedures include investigative and diagnostic methods as well as medical and surgical treatments. Percutaneous techniques are advantageous because they are minimally invasive, and therefore present a reduced risk to the patient when compared with invasive surgeries requiring open access to tissues within the patient's body.
Catheters and sheaths are typically used to access internal sites by entering the patient's body through an incision or other entry point to the peripheral vasculature and navigating through the torturous paths of the vascular system to the target site. Tools, cameras illumination sources and transducers can be deployed through the catheters and sheaths enabling a physician to inspect the site, take biopsies, implant devices, repair damage and perform numerous other tasks often on an outpatient basis.
Minimally invasive percutaneous approaches have also presented an opportunity for localized delivery of therapeutic agents. Localization facilitates improved treatment since the agent may be delivered directly to a target site, (for example, an organ) thereby avoiding “first pass” degradation in the liver. The agent may therefore exhibit an improved therapeutic effect when compared with the same agent administered orally, intravenously or via the intramuscular route. Moreover, where the therapeutic agent has benefit to the target site but is likely to be toxic to other organs or tissues, localized delivery can minimize the exposure and hence the risk presented to cells in other parts of the body. An example is where a cytotoxic drug is to be delivered to a cancerous organ, but it is desired to minimize or prevent exposure of healthy organs to the drug.
Various devices and methods to facilitate the percutaneous delivery and collection of fluids to organs and tissues of the human body have been described in the art. Typically, these devices and methods include a first catheter to deliver a fluid to an organ or tissue and a second catheter to collect fluid exiting the organ or tissue. The collected fluid may be returned to the organ, or discarded as waste outside the body.
While devices and methods of the prior art appear to address the theoretical requirements of percutaneous delivery and collection of fluids, Applicant has found that they are of little practical use in the clinic. In particular, difficulties are encountered in maintaining sufficient flow rates of fluid through a collection catheter. As will be appreciated by the skilled person, where a collection catheter is positioned in a vein, venous pooling, tissue damage and possible death of the subject can result from low flow rates. Low flow rates via a collection catheter may also severely limit the ability to deliver the therapeutic agent via a delivery catheter given that in order to maintain fluid balance the volume of fluid entering and exiting should be substantially equal.
Applicants have identified a further problem with devices and methods of the prior art in that damage to vessel walls may also be noted after catheterization of vessels. Where the catheter is a collection catheter, partial or complete occlusion is sometimes observed during use. Yet a further problem exists in that catheters often move from the position in which they are deployed.
It is an aspect of the present invention to overcome or alleviate a problem of the prior art by providing devices and methods capable of maintaining the flow of fluid via the collection catheter. The methods and devices may also minimize vessel wall damage, occlusion of the catheter lumen, and movement of a catheter after placement.
The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.